Hot top liner and refractory ring combination for use with metal casing that is hot

ABSTRACT

A combination of an exothermic insulating liner and refractory ring for use in a metal hot top casing that is hot. The liner composition comprises by weight from 4 - 6% low water content asbestos, from 4 - 6% high water content asbestos, from 65 - 75% sand, from 12 - 16% silica flour and from 3 - 6% resin binder; and the refractory ring composition comprises by weight from 6 9% asbestos, from 87 - 90% sand and from 3 - 4.5% resin binder.

United States Patent McCarthy 51 May 2, 1972 HOT TOP LINER AND REFRACTORY 1 References Cited RING Qg T WITH UNITED STATES PATENTS METAL A G THA IS 3,072,981 1/1963 Davidson ..l06/38.35 X [72] Inventor: James F. McCarthy, Mars, Pa. 3,297,296 1/1967 Edstrom et al 3,478, 11 h t 1. [73] Assignee: The Susquehanna Corporation, Fairfax, 999 C arman e a 249/;

Primary ExaminerLorenzo B. Hayes [22] Filed: Feb. 5, 1970 og 7 [21] Appl. No.: 9,084 57 ABSTRACT A combination of an exothermic insulating liner and refracto- [52] [1.8. CI. ..106/38.25, 106/3822, 249/197, ry ring for use in a metal hot top casing that is hot. The liner 249/202, 260/29.3, 260/38, 260/39 SB composition comprises by weight from 4 6% low water con- [51] Int. Cl ..B28b 7/36 n asbestos, fr m 4 6% hig water c n asbestos. m [58] Field 0! Search ..106/38.22, 38.23, 38.24, 38.27, n m 12 16% ilic flour and from 3 6% resin binder; and the refractory ring composition comprises by weight from 6 9% asbestos, from 87 90% sand and from 3 4.5% resin binder.

10 Claims, No Drawings HOT TOP LINER AND REFRACTORY RING COMBINATION FOR USE WITH METAL CASING THAT IS HOT BACKGROUND OF THE INVENTION This invention relates to a combination of a hot top liner and a refractory ring, and the composition for each, for use in a metal hot top casing that is hot.

As is well understood in the art, hot top casings are used in conjunction with ingot molds in the casting of metal ingots such as steel ingots. The purpose of these hot tops is to provide a reservoir of molten metal in the casing to feed the pipe or shrinkage cavity in the ingot mold as it tends to form during solidification. In this manner, solid or nonporous ingots can be produced without the necessity of scrapping a portion of the ingot from the mold and only the top portion containing a minor amount of steel must be cropped.

The latest type of hot top casing in commercial use today for the casting of big end up ingots comprises a metal casing, generally a one-piece casing, having an insulating or exothermic liner on the inner surface of the casing and a refractory ring around the bottom of the casing. The hot top casing itself is reuseable but the insulating liner and refractory ring must be replaced after each use, that is, after the casting of each ingot. The liner and refractory ring are made generally from relatively low cost compositions having good heat insulation or exothermic properties, and the compositions for the liner and the refractory ring are usually preformed into self-supporting slabs or sleeves for the liner and into rings to fit a particular casing with which they are to be used. After each use of a hot I top casing, the remnants of a used liner and refractory ring,

which are at least partially disintegrated during the casting operation, are removed from the metal casing and replaced by a new liner and refractory ring so that a casing is ready for use in a subsequent ingot pouring operation.

Many compositions have been proposed for hot top liners to overcome the characteristic difficulties of prior art materials which include insufficient insulating capacity, contamination of the ingot, and others. Also, many of the premolded insulating materials or liners which are inserted in the casings as insulating surfaces are very fragile and readily broken. In this instance, damage results to the casing by contact of the molten metal.

To perform most satisfactorily, insulating liners should have good resistance to breakage at ambient temperatures to permit good storage and handling; should have a measure of deformability to permit use in non-uniform casings; should have good insulating and a measure of exothermic properties to permit minimum heat loss from the reservoir of molten metal; shouldbreak down or lose structural integrity after use without contaminating a poured ingot to permit easy removal from an ingot and casing, and should be a low cost item to permit economy of operation.

Many compositions have been proposed for refractory rings to overcome the characteristic difficulties of prior art materials such as cracking or breaking and failure of a ring to protect a hot top casing from contact with molten metal and failure to seal the molten metal to the ingot mold wall at the top of the mold. When a refractory ring is prepared having a thermal conductivity which is too low, the molten metal in an ingot mold will not seal off rapidly enough at the top of the mold around the ring, and then molten metal will pass the ring causing failure of the casting by welding the metal hot top casing to the ingot or ingot mold. When the thermal conductivity of a refractory ring is too high, the molten metal may be cooled during the pour too rapidlyat the throat or top portion of the ingot mold causing the throat section to seal off. This prevents the reservoir of molten metal in the hot top casing from feeding the solidifying metal in the ingot mold causing sink holes or pores in the ingot and unnecessary ingot loss in the casting operation.

The problems involved in preparing proper compositions for hot top liners and refractory rings, which will perform their desired functions more than adequately, result from at least two things. It has been recognized that the hot top liners and the refractory rings perform separate and individual functions, and accordingly, compositions were prepared for each to meet the requirements of the functions of each. It has not been recognized, however, that a liner and a refractory ring must also perform as a unit to carry out their individual functions properly.

Also, the manner in which liners and refractory rings are used by the industry in every day practice has not been considered sufficiently. Since the advent of the use of metal hot top casings without insulating brick linings for casting steel ingots, it is the general practice to have a quantity of metal casings stored adjacent to the area where the ingot pouring will take place. After a pour is completed and the metal in a hot top casing has solidified sufficiently, the casing is stripped from the ingot mold, cleaned to remove remaining parts of the liner and ring and returned to storage in the area where a new liner and refractory ring are fitted to the casing for subsequent reuse. As a result, quite frequently liners andrefractory rings may be refitted to hot top casings which are still very warm from prior use, and in other instances, liners and refractory rings may be fitted to hot top casings which are cold.

Since both a hot top liner and a refractory ring must supply a combination of insulating properties and exothermic proper ties to perform properly in their functions of keeping the metal molten within the casing and sealing the metal to the mold at a proper rate at the bottom of the casing while both protecting the metal casing from contact with the molten metal and degrading during use for easy removal, the compositions for both the liner and the ring contain materials which will burn or otherwise provide an exotherm when contacted by molten metal. As a'result, when present liners and rings are refitted to casings that are hot, the liners and rings may begin to degrade or smoke prior to use in a casting operation. This causes the materials to exhaust their exothermic properties before they are needed and makes the resulting liners and rings too frangible to withstand the rough handling in the assembly to an ingot mold and subsequent contact with molten metal. Accordingly, the metal casing, the ingot mold, the ingot or all three may be damaged or lost.

It is clear, therefore, that a combination of a hot top liner and a refractory ring which may be used successfully with a hot top metal casing that is hot is a worthwhile advance in the an.

SUMMARY OF THE INVENTION In accordance with this invention, there is provided a new and novel combination of a hot top liner and refractory ring for use with a metal hot top casing that is hot comprising, in combination, a hot top liner having a composition by weight consisting essentially of:

a. from about 4% to about 6% low water content asbestos;

b. from about 4% to about 6% high water content asbestos;

c. from about 65% to about 75% sand;

d. from about l2% to about 16% silica flour; and

e. from about 3% to about 6% of a resin binder;

and a refractory ring having a composition by weight consisting essentially of:

f. from about 6% to about 9% asbestos;

g. from about 87% to about 90% sand; and

h. from about 3% to about 4.5% of a resin'binder.

Other embodiments of the invention are the combination as described further characterized by the low water content asbestos being amosite asbestos and/or the high water content asbestos being chrysotile asbestos.

Another embodiment of the invention is a combination of hot top'liner and refractory ring as defined further characterized by the sand for the hot top liner composition having an American Foundry Standard grain fineness number of about 1 l0.

Another embodiment of the invention is the combination as defined further characterized by the sand for the refractory ring composition having an A.F.S. grain fineness number of about 133.

Another embodiment of the invention is the combination as defined further characterized by the silica flour having a particle size smaller than about 200 mesh.

Still another embodiment of the invention is the composition as defined further characterized by the asbestos for the refractory ring composition being amosite asbestos.

The combination of hot top liner and refractory ring of this invention has many advantages. The individual parts, or the liner and the refractory ring, have considerable deformability and resilience at ordinary temperatures which provide good resistance to breakage and damage during handling and storage. When the combination of hot top liner and refractory ring is used in a hot top casing, no damage results either to the liner or the refractory ring as a result of the hot metal casing and no smoking, prebuming or preexotherm of either the liner or the refractory ring occurs. In use in a casing during a pour ing operation, the hot top liner provides good insulating characteristics and sufficient exotherm to maintain the needed reservoir of molten metal within the hot top casing to provide good ingots free from porosity; and the refractory ring has the required amount of thermal conductivity and exothermto prevent cracking and breaking of the ring; to provide a metal seal at the right rate without permitting welding of the hot top casing to the head of the mold; and there is no metal freezing within the throat of theingot preventing proper filling of the ingot from the hot top reservoir. When using the combination of hot top liner and refractory ring of this invention, the overall design of the hot top casing can .be changed to reduce the area of the opening into the ingot mold from the usual 50 percent of throat opening to 40 percent or less; and ingot loss due to cropping of the solidified material within the hot top casing is 7 percent or less.

DESCRIPTION OF PREFERRED EMBODIMENTS In the combination of this invention the hot top liner and the refractory ring may be a one'piece structure or a multipiece structure depending upon the design and shape of the hot top casing with which they may be used. In general, a refractory ring is a molded one-piece article and a hot top liner may be molded panels which are inserted separately within the hot top casing or a molded group of panels which are hinged by wire, paper or other means so that it can be stored flat and made into a proper rectangular or other shaped structure for insertion within the hot top casing. One-piece liners molded into a desired shape are known and used also.

The combination of this invention of a hot top liner and refractory ring is for use in metal hot top casings without insulating firebrick linings; however, the combination would find utility in lined casings also. The combination of this invention may be used in the more common one-piece or multi-piece metal hot top casing and is for use in hot top casings which are at a temperature of 100F. or greater; however, in limited applications, the combination of this invention or a hot top liner or refractory ring thereof may be used separately with good success in hot top casings having a temperature below lF..

The hot top liner of this invention is one having a composition by weight consisting essentially of:

a. from about 4% to about 6% low water content asbestos;

b. from about 4% to about 6% high water content asbestos;

c. from about 65% to about 75% sand;

d. from about 12% to about 16% silica flour; and

e. from about 3% to about 6% of a resin binder.

In this tailored formulation for a hot top liner, it'is important to have present both a low water content asbestos and a high water content asbestos. Although it is not understood clearly, the particular combination of low water content asbestos and high water content asbestos in aliner of this invention permits the liner to be in contact with a hot metal casing without resulting damage or loss of properties to the liner, the refractory ring or the combination.

Low water content asbestos materials generally have a combined water content of from about 3% to about 6% and amosite, tremolite, crocidolite and anthrophyllite asbestos materials, as well as mixtures of these and other materials, are representative of low water content asbestos. Of these, the use of amosite asbestos for the low water content asbestos is preferred. High water content asbestos materials generally have a combined water content of from about 12% to about 18% and chrysotile asbestos materials, as well as mixtures of these and other materials, are representative of high water content asbestos.

The asbestos fibers for both the low and high water content materials may substantially be of any length, and any of the shorter length materials which are more economical may be used. The fibers used, however, should be sufficiently long to provide some strength to the structure. I

The sand used in the liner composition may be of substantially any particle size or mixture of particle sizes readily available; however, it is preferred that the sand for the hot top panel composition have an A.F.S. grain fineness number of from about 75 to about 200, and of these, an A.F.S. grain fineness of about 1 I0 is more preferred.

The silica flour used in the liner composition may be of any of the readily available silica flours and it is preferred in accordance with this invention that the silica flour have a particle size smaller than about 200 mesh. 7

The silica flour, which is amorphous, as distinguished from the sand, which is crystalline, provides improved insulation properties. The sand provides improved processing properties in terms of more rapid filtration, faster drying and faster cure than would be obtained with the amorphous silica flour alone.

The resin binder of this invention may be any of the inexpensive readily available resin binders which are thermosetting such as ureaformaldehyde, phenolformaldehyde resins and others from which an aqueous or solvent dispersion may be prepared. Thermoplastic resins from which dispersions may be prepared and which have good high temperature resistance may be used also. In accordance with this invention, it is preferred that a phenolformaldehyde resin binder be used.

The refractory ring of the combination of this invention is one having a composition by weight consisting essentially of:

a. from about 6% to about 9% asbestos;

b. from about 87% to about 90% sand; and c. from about 3% to about 4.5% ofa resin binder.

The asbestos for the refractory ring composition can be any of the well-known asbestos having either high or low water content or mixtures thereof, such as amosite, chrysotile or others such as indicated previously for the liner. In accordance with this invention, it is preferred that the asbestos for the refractory ring be amosite asbestos because of its availability and economy.

The sand for the'refractory ring may be any of the readily available sands having varying compositions of particle size and concentrations of particle size; however, it is preferred in accordance with this invention that the sand for the refractory ring composition have an A.F.S. grain fineness number of from about 75 to about 200, and of these, a grain fineness number of 133 is more preferred.

The resin binder for the refractory ring may be any of the resin binders described previously for the liner composition; and of these it is preferred that the resin binder be a phenolfonnaldehyde resin capable of being prepared in dispersion form.

The hot top liners and refractory rings of this invention may be prepared in any manner well-known for, the preparation of similar articles. In general, a water slurry of the components of the composition are prepared using a large excess of water, and then the slurry is laid down on a screen or other porous mold which has been shaped to define a desired liner or ring configuration. Following this, excess water is removed from the article by vacuum or pressure and the partially dried article within the mold is subjected to heat at a temperature of from about 250 to 400F., preferably about 350 to 390F., for a period of time sufficient to dry the panel and to cure the resin binder. Other suitable curing methods may be used for the resin binder also. After this, the dry liner or ring may be stored for shipment or use as needed.

A hot top liner was prepared in accordance with this invention by mixing a weight percent composition of 4.8% amosite asbestos fibers, 4.8% chrysotile asbestos fibers, 71.4% sand having an A.F.S. grain fineness number of about 110, 14.3% silica flour having a particle size smaller than about 200 mesh and 4.8 percent of a phenolformaldehyde resin in a suitable container with an excess of water to prepare a slurry. Following this, the slurry was passed into a flat screen mold prepared in the proper shape to make a liner having joined panels approximately 2 feet long, 8 inches wide and 1 inch thick. Excess water was removed from the mold by pressure and the joined panels cured in an oven at a temperature of from about 350F. to 390F. for a period of about 2 hours. The hot top liner having joined panels was removed from the oven and mold after curing of the binder was substantially complete.

A refractory ring was prepared in accordance with this invention by mixing a weight percent composition of 88.5% sand having an A.F.S. number of 133, 7.7% amosite asbestos fibers, and 3.8% phenolformaldehyde resin with water to form a slurry. The slurry was molded in the same fashion as the liner to prepare a refractory ring to fit the bottom portion of a metal hot top casing and overlap the bottom edge of the molded hot top liner when inserted in the casing.

When the liner is inserted in a metal hot top casing having a temperature of approximately 150F. and the refractory ring is placed on the bottom portion of the casing and held there with clips, the inner surface of the hot top casing is covered completely and the ring covers the bottom edge of the casing and inserted liner and extends approximately 2 inches beyond the outside of the'casing. There is no evidence of smoking or other degradation of the liner or ring after approximately 1 hour. When the assembled hot top casing is placed on the top of a big-end-up ingot mold and a steel ingot is poured, a good metal seal is obtained between the ring and the ingot mold and the hot top feeds the ingot. The used casing strips easily from the ingot and the remnants of the liner and ring strip easily from the casing and ingot.

I claim:

1. A combination of a hot top liner and a refractory ring for use with a metal hot top casing that is hot comprising, in combination, a hot top liner having a composition by weight consisting essentially of a. from about 4% to about 6% low water content asbestos having a water content of about 3% to about 6%; b. from about 4% to about 6% high water content asbestos having a water content of about 12% to about 18%;

c. from about 65% to about 75% sand;

d. from about 12% to about 16% silica flour; and

c. from about 3% to about 6% of a resin binder which can be dispersed in water and solvent systems; and a refractory ring having a composition by weight consisting essentially of f. from about 6% to about 9% asbestos;

g. from about 87% to about 90% sand; and

h. from about 3% to about 4.5% of a resin binder which can be dispersed in water and solvent systems.

2. The combination of claim 1 further characterized by said low water content asbestos being amosite asbestos.

3. The combination of claim 1 further characterized by said high water content asbestos being chrysotile asbestos.

4. The combination of claim 1 further characterized by the low water content asbestos being amosite asbestos and the high water content asbestos being chrysotile asbestos.

5. The combination of claim 1 further characterized by the asbestos for the refractory ring composition being a amosite asbestos.

6. The combination of claim 1 further characterized by the sand for the hot top liner composition having an A.F.S. grain fineness number of about 1 10.

7. The combination of claim 1 further characterized by the sand for the refractory ring composition having an A.F.S. grain fineness number of about 1 33.

8. The combination of claim 1 further characterized by the resin binder for the hot top liner composition being a phenolformaldehyde resin. 1

9. The combination of claim 1 further characterized by the resin binder for the refractory ring composition being a phenolformaldehyde resin.

10. The combination of claim 1 further characterized by the silica flour having particle size smaller than about 200 mesh. 

2. The combination of claim 1 further characterized by said low water content asbestos being amosite asbestos.
 3. The combination of claim 1 further characterized by said high water content asbestos being chrysotile asbestos.
 4. The combination of claim 1 further characterized by the low water content asbestos being amosite asbestos and the high water content asbestos being chrysotile asbestos.
 5. The combination of claim 1 further characterized by the asbestos for the refractory ring composition being a amosite asbestos.
 6. The combination of claim 1 further characterized by the sand for the hot top liner composition having an A.F.S. grain fineness number of about
 110. 7. The combination of claim 1 further characterized by the sand for the refractory ring composition having an A.F.S. grain fineness number of about
 133. 8. The combination of claim 1 further characterized by the resin binder for the hot top liner composition being a phenolformaldehyde resin.
 9. The combination of claim 1 further characterized by the resin binder for the refractory ring composition being a phenolformaldehyde resin.
 10. The combination of claim 1 further characterized by the silica flour having particle size smaller than about 200 mesh. 